The general view commonly accepted so far even by those duly skilled in the art that regular dry batteries are not rechargeable. This view however, had substantially been valid until relatively small transistorized, or rather semiconductorized and battery-operated radio and other sets of very low power consumption in the range of only 10 to 25 mA appeared on the market. The above mentioned view of dry batteries being not rechargeable is still valid for batteries that are in use mainly for lighting purposes in electric appliances the current consumption of which generally lies between 0.1 to 0.3 A for normal operation.
For the purpose of recharging mainly nickel-cadmium (NiCad) accumulators and similar per se rechargeable batteries a large number of charging devices have become known and also available on the market. Such known devices are however, relatively costly and the same applies to the rechargeable accumulators as well. Besides this, the available chargers are not suitable for the regenerative recharging of regular dry batteries since they may cause serious damage to them, and using the known charger for this purpose may occasionally lead to an explosion of some of the batteries that had been inserted for recharging. Hence, the known devices of the kind referred to above, generally bear a warning notice included in their operating instruction indicating the above risk expressively.
Today, some of the leading manufacturers sell their more valuable miniaturized radio and other sets of both mains and battery operation designed and constructed for more sophisticated consumers with built-in circuitry for the regenerative recharging of the dry batteries inserted. Such built-in AC adaptors are constructed and operate as charger transformers. Hence, their cost of manufacture is substantially high and such devices as independent, purposeful sets have hitherto not become known and available to public.
Thus, the main object of the present invention is to provide a novel, improved charging set designed and constructed primarily for the purpose of the regenerative recharging of dry batteries commonly in use that is easy and very cheap with respect to its cost of manufacture especially when produced in large quantities whereby its selling price can be kept at a substantially low level.
Another equally important object of the present invention is to provide a charging set for regular dry batteries that is extremely easy to handle and is despite of its simple design and construction absolutely shock-proof under operational conditions.
The basic idea of the present invention is that for the purpose as set forth above, a charging set without a costly transformer unit, i.e. by using a charging rectifier that includes only cheap passive current-limiting and rectifying circuit elements can be developed only when substantial protection through preventing the user from access to any naked and possibly live component part of the charging set during its handling and operation is provided for. To achieve the desired objects it is essential to fulfill the above pre-conditions at the same time. Although the charging rate is limited, depending on the particular type and number of dry batteries to be recharged simultaneously, to rates between 1 to 7 mAs that can be regarded as absolutely not dangerous to the human organism, the metallic body or a run-down exhausted or fault dry battery may show, when connected in series, a live voltage of 110 to 150 V against the earth when being inserted in a plugged-in charging set having no charger transformer. Hence, for the sake of sufficient prevention of accidents any possibility of touching such areas of the inserted battery and also of any naked live component part of the built-in charging rectifier must be ultimately excluded in the plugged-in operational state of the charger set.